I have a promise RAID controller, and have had no problems (why did i just say that) with it thus far.
The speed boost is definatly noticeable; being able to copy files while listening to mp3s and surfing is very tolerable with raid 0.
with 2 channels i have 2 partitions; i can use winimage and rebuild win98 in 4:30 mins
your best bet is to stick with an identical drive.